This study aims to obtain descriptive pharmacodynamic and pharmacokinetic data for Antegren in multiple sclerosis patients following a single intravenous dose of 1.0, 3.0, or 6.0 mg/kg. A specific goal is to obtain data describing changes in alpha 4 integrin saturation during the period of 4 to 14 weeks following a single intravenous Antegren infusions.